Field of the Invention
The present invention relates to an image reading apparatus with an original size detection sensor.
Description of the Related Art
Conventionally, image reading apparatuses are known which have a moving original reading function of stopping an optical scanning unit, which irradiates an original with light, at a predetermined original reading position to read originals one by one while moving them. Some of these image reading apparatuses have a mixed-size mode in which originals of different sizes are placed on an original tray and successively read while being moved. In the mixed-size mode, original sizes vary from one original to another, and accordingly, an original size detection means is provided on an original conveying path. Zooming, allocation of image data storage memory, and so forth are performed according to an original size detected by the original size detection means.
As the original size detection means, there have been proposed one which has an original size detection sensor, and one which detects an original size from read image data (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. 2013-102267). There has also been proposed one which compares a set original size with an original size detected from read image data, and when they are different, deletes the original size detected from the read image data (see, for example, the specification of Japanese Patent No. 4905268).
However, in an image reading apparatus equipped with an original size detection sensor, there is a need to place mixed-size originals on an original tray with edges aligned on any one side in the mixed-size mode, and defying this leads to a problem that an original size is erroneously detected, and a poor image is generated.
For example, as shown in FIG. 14A, when a large original that is large in size and a small original that is small in size are placed on the original tray with left side edges aligned, not right side edges that are supposed to be aligned, the original size detection sensor may erroneously detect the small original as a large original. Specifically, when originals are placed on the original tray with left side edges aligned, and a copy is made with a setting that selects a print sheet size according to an original size, an image situated at an upper-left corner of a sheet for a large original may be output as shown in FIG. 14C although an output shown in FIG. 14B is expected. Also, when a print sheet size is set to a size for a small original, and a copy is made with a setting that zooms a read image according to a sheet size and performs printing, a reduced image may be output as shown in FIG. 14D.
On the other hand, in an image reading apparatus that detects an original size from read image data, there is no need to align originals even in the mixed-size mode, but it is impossible to determine an original size before reading of the original is started. Namely, a timing at which an original size is determined comes later than a timing at which an original size is determined based on a result of detection by the original size detection sensor.